By far I would have to say that the diamond goby is the coolest of them all. I loved to watch mine dig in the sand creating his cave home. He seemed to have a great personality, and was very active and helped keep the sand clean!!
Here is mine...
my favorite is the firefish goby. it has lots of color everywhere. mine has red dark red, blue, aqua, alittle purple. and its really cool. and my second favorite is the yellow watchman goby which im getting soon.